I actually have to agree with the slightly analytical bit. But I also agree with lestatar, they are very fun. iM-590 are analytical in the since that are more neutral than natural. Vocals are crisp rather warm. Where the iM-590 differs from the analytical sound though is the bass. It is deep and has good impact making surprisingly fun. The treble is also has some sparkle which makes it bright. If the A151 is what everyone says it is, it is the opposite of the iM-590. Warm natural vocals, laid back bass, and tame low sparkle treble. If anything, I would say the A151 is probably the more boring of the two despite the fact it is not analytical. That is just a guess though, I will have to wait until tomorrow to find out for myself....SNIPPED...

^ This. Best description of the i590s sound signature I have read - certainly I could not have said it any better.

Got the A151 this morning. I have only had them an hour or so it is a bit early to draw too many conclusions, but my first impressions nonetheless.

The cable is amazing. I know that has been said before, but it is worth repeating. If the iM-590 has the most microphonic cable of all my IEM's then the A151 is the least microphonic. And the cable is so flexible. I thought I could live the stiff UE TripleFi 10 cable, but after this it is going to be hard to go back.

Sadly, the A151 seems to be a little big for my small ears. The back presses against the back of my ear which makes them a little uncomfortable. Please keep in mind that this is just me though, I am pretty sure they would very comfortable if it were not for having small ears.

The bass, or lack there of, was a bit of a surprise to me. I have yet to buy a pair of earphones that left craving more bass, but I guess there is a first time for everything. I am sure it is nothing a little EQ could not fix, but it is something I would keep in mind if you are a bass lover.

I do not really have anything to say about the mids yet.

Treble is surprising pleasant. I was afraid it would be boring, but it is actually quite enjoyable. I imagine this is largely do to the clarity of balanced armatures. The treble sound quality is easily superior to the iM-590.

Sound stage is kind of average.

In the end, I do not feel like the A151 is good enough to justify the price over the iM-590 in sound quality alone. I think sound signature should be the deciding factor. The iM-590 is a lot more "fun" where the A151 is more bland, but detailed. Those are just early thoughts though.

Oh, and while I do not listen to classical music, after hearing a little bit of classical on a couple of rock album on the A151 I might just have to give classical another shot!